Many medical conditions can cause the partial or complete occlusion of blood vessels, leading to an insufficient blood supply to tissues and organs. For example, atherosclerosis (also known as arteriosclerotic vascular disease) is a condition in which artery walls thicken and harden due to a build-up of plaque forming fatty materials such as cholesterol. These atheromatous plaques can eventually rupture, with clots forming over the ruptures inside the artery lumen. The clots usually heal and shrink but this process can lead to a narrowing (stenosis) or, worse still, complete closure of the artery. Severe consequences of plaque rupture include aneurysms, myocardial infarction (heart attack) due to a blood clot in the coronary artery and strokes due to a blood clot in an artery to the brain.
Blood clots in veins (venous thromboses) can have equally severe consequences. Superficial venous thromboses generally only cause discomfort but deep venous thromboses (DVTs) that form in the deep veins of the legs or in the pelvic veins can not only block the vein in which they are situated but can also potentially break free from the vein and travel towards the heart and lungs, thereby causing a myocardial infarction or pulmonary embolism.
Tumours are another cause of vascular obstruction, whether benign, pre-malignant or malignant. Hemangiomas, lymphangiomas and glomus tumours are examples of benign tumours that are found in and around blood vessels. Angiosarcomas and Kaposi sarcoma are examples of malignant tumours.
Percutaneous surgical procedures involve insertion of a therapeutic probe, typically a catheter mounted on a guidewire, through an incision made in the skin of the patient. The probe can be guided to a therapeutic site in the body via the circulatory system of arteries and veins, thereby reducing the need to cause more extensive trauma to the patient by adopting more traditional open surgical techniques.
Prior surgical methods for widening the lumen of blood vessels, and in particular for treating atherosclerosis, include balloon angioplasty, laser catheter angioplasty and the use of plaque cutting devices. Balloon angioplasty involves inflating a balloon at the site of blockage in order to compress the atheromatous plaque into the wall of the blood vessel, thus enlarging the lumen of the blood vessel. However, use of this technique involves a high risk of restenosis of the blood vessel due to the reoccurence of arterial plaque. Furthermore, since a relatively high mechanical force is being applied to the plaque there is a risk of plaque dislodgement or of plaque rupture rather than compression, leading to the release of the plaque itself or of plaque contents into the blood stream, which can potentially cause a stroke by embolisation as well as causing other complications. The relatively high mechanical force imparted by the device can also potentially cause the vessel wall itself to rupture.
Laser catheter angioplasty involves inserting a fibre optic cable connected to a laser energy source into the blood vessel and pulsing the laser to vapourise a portion of the plaque. There are several problems associated with laser procedures, most notably the difficulty in locating the fibre optic probe in the correct position and the high risk of blood vessel wall perforation due to the high energy levels used.
Plaque cutting devices use means such as scissors or rotating blades to cut the plaques away from the artery wall. However, the use of such devices runs the risk of damaging and/or perforating the blood vessel wall.
Hence, there exists a need for an improved device which can be used to remodel the internal surface topography of obstructed hollow anatomical structures such as blood vessels of a range of diameters from large to small. In addition, there exists a need for such devices that can be used percutaneously and targeted to sites within the body of a patient that are remote from the operator and which can reliably dilate the lumen of blood vessels at those sites.